Highlights of Spanish Astrophysics VII, Proceedings of the X Scientific Meeting of the Spanish Astronomical Society (SEA), held in Valencia, July 9 - 13, 2012, Eds.: J.C. Guirado, L.M. Lara, V. Quilis, and J. Gorgas., pp.926-931 (2013).
Obtaining images near the diffraction limit of large telescopes is key to the success of many observational projects, but requires either adaptive optics (AO) equipment or the application of speckle techniques. While AO is expensive, complex, and requires long development times, speckle imaging is far easier to implement. However, the most frequently used image reconstruction techniques, like simple shift-and-add and the related lucky imaging, suffer from important limitations in sensitivity and efficiency. Here, we present an improved version of the speckle holography technique, that is particularly optimized for crowded fields. Holography is highly efficient, generally supersedes lucky imaging, and can rival and even surpass AO imaging, particularly at short wavelengths. It is a highly flexible technique and can be used with a broad range of existing instruments, thus imbuing them with novel high angular resolution capabilities at no (or hardly any) additional cost. Speckle holography makes high-angular resolution imaging available whenever an imaging instrument offers fast readout capability combined with adequate sampling of the image plane.